Groovy module

Magnolia Groovy module adds Groovy capabilities to Magnolia. Groovy is a popular dynamic language for the JVM. To know more about it, please visit the Groovy official website which has plenty of tutorials and excellent documentation both for beginners and advanced users of the language.

The module provides a web based Unix-like console where you can access contents in Magnolia repositories in a "groovish" way, a scripts repository where you can store your scripts and the ability to plugin Groovy classes into Magnolia at runtime, without the need for deploying them and restarting the servlet container. All these tools make for a more agile approach to coding and maintaining Magnolia based websites.

Installing

<dependency>
  <groupId>info.magnolia</groupId>
  <artifactId>magnolia-module-groovy</artifactId>
  <version>2.4.8</version>
</dependency>

• magnolia-module-groovy.jar

Usage

Repository data navigation simplified

Thanks to the . (dot) notation and other handy shortcuts such as .nodes (alternatively .children), .properties, .metaData and .parent you can read any content node and property, change their values, create nodes and delete them, all with clean, concise syntax. The module is shipped with some preinstalled scripts that demonstrate most of these features. As an example, here is how to navigate to and print the node data named title:

session = ctx.getJCRSession('website')
node = session.getNode('/travel')
node.about.title

One noticeable thing about the above snippet is that it is all you need to write: no imports, no need to catch exceptions, etc. Compare it to the Java code that achieves the same result.

import info.magnolia.context.MgnlContext;
import javax.jcr.Node;
import javax.jcr.RepositoryException;
import javax.jcr.Session;

public class Test {
    public static void main(String[] args) {
        try {
            Session session = MgnlContext.getJCRSession("website");
            Node node = session.getNode("/travel/about");
            String value = node.getProperty("title").getString();
            System.out.println(value);
        } catch (RepositoryException e) {
            e.printStackTrace();
        }
    }
}

And, most importantly, with Groovy you do not need to deploy your class and restart the server. As an additional bonus, when using the Groovy Unix-like shell which comes with the module, when you navigate a repository, by calling the print() method on a node its children and properties are shown in the output, giving you an overview of the data structure. The screenshot below illustrates this.

Being able to navigate a repository data like this can come in handy, for instance, when writing and testing your own scripts or trying things out. Or when you need to use the Rescue App  because the Magnolia UI, for whatever reason, is not available.

As node here is basically an instance of a JCR Node coated in a special "groovysh" wrapper, you to call any of the Node interface methods and take advantage of the Groovy goodies at the same time.

node.about.properties.each { println it.name } 
println node.about.parent //(this can be null)

If you want to print out all node properties but jcr ones, you can do:

node.about.properties.findAll { !it.name.startsWith('jcr:') }.each{ println it.name }

Built-in Help

Type help (or ?) followed by Enter  to view the built-in help (including keyboard shortcuts) for the Groovy shell.

Autocompletion & Keyboard Shortcuts

Autocompletion in the Groovy console:

• Start writing a variable name and press Tab to autocomplete available variables in script context.
• Press Tab Tab to discover available variables in script context.
• Type . (dot) after a context variable and press Tab to autocomplete method names.
• Type . (dot) after a context variable and press Tab Tab to discover method names.

The ctx context object is always available. In Groovy it represents MgnlGroovyConsoleContext, a special instance of Magnolia's Context.

Create and update properties

It is also possible to assign values to properties or create new ones.

node.foo = 3.14d
node.bar = true
node.baz = 'some text'
node.qux = 100

This will assign the values on the right hand side to the properties on left hand side. Should those not exist, they will be automatically created. Moreover, the correct type will be detected based on the value assigned (Boolean, String, Long or Double).

Use Groovy classes instead of Java classes

This feature allows you to virtually replace every Magnolia Java class with a Groovy one. Although not a major issue for most tasks, due to its dynamic nature Groovy is slower than Java. Nevertheless, replacing classes can come in handy in situations where you cannot deploy and restart the server, but need to quickly fix or add a piece of logic.

The Groovy module ships with a sample class my.commands.GroovyMailCommand that sends an email. Here is how you could use it to create a new scheduled job on-the-fly using a Groovy command and the Scheduler module.

The GroovyMailCommand is accessible in Dev > Groovy /my/commands/GroovyMailCommand .

package my.commands
import info.magnolia.commands.*
/*
* This groovy class is an example that serves to show how it can be used as a replacement of a traditional Java class on the fly.
*/
public class GroovyMailCommand extends MgnlCommand {

    public boolean execute(Context ctx) {

    def ant = new AntBuilder()
    def buildname = ctx.get('buildname')
    ant.mail(mailhost:'mailhost', mailport:'25', subject: ctx.get('subject')){
      from(address:ctx.get('from'))
      to(address:ctx.get('to'))
      message("The ${buildname} nightly build has completed")
      }
    }
}
//this is for testing only
ctx.put('from', 'foo@mail.com')
ctx.put('to', 'bar@mail.com')
ctx.put('subject', 'hello')
ctx.put('buildname', 'TEST123')

if(new GroovyMailCommand().execute(ctx)) println 'mail sent successfully'

 Replace mailhost with your SMTP server address.

Create a command configuration in the Configuration app as shown below. We added it to the Mail module in /modules/mail/commands/default, but you can add it to your own module or another of your choice. Specify the fully qualified name of the Groovy class (matching the path in the repository where it is saved my.commands) as if it were a plain Java class (which it actually is).

Create a scheduled job configuration referring to the command in the Configuration app > /modules/scheduler/config/jobs. The parameters will be used at runtime by the Groovy script.

Replace the from and to email addresses with actual addresses.

You can use this command to replace a similar Java command at runtime. Or you can edit it and have it compiled and replaced on-the-fly (a kind of class hot deploy). This relies on the Magnolia observation mechanism. Every time the value of the class node data changes the Groovy class will be recompiled.

Rescue App

The MgnlGroovyRescueApp is a special Vaadin app that can be used to bypass the Magnolia filter chain. This is useful when you need to perform rescue operations on a corrupted Magnolia instance or when the Magnolia UI is not loading. To enable the servlet you must explicitly comment out the Magnolia filter chain in the web.xml file and register the Groovy Rescue App. 

All operations performed in the Groovy Rescue App are executed in system context, meaning no security restrictions are enforced. This might expose your data to risk of irreversible damages if you are not aware of what you are doing. In other words, use it at your own risk.

Register the Groovy Rescue App

1. Stop Magnolia
2. Open /<CATALINA_HOME>/webapps/<contextPath>/WEB-INF/web.xml in a text editor.

3. Comment out the filter and filter-mapping sections:

   <!--
   <filter>
      <display-name>Magnolia global filters</display-name>
      <filter-name>magnoliaFilterChain</filter-name>
      <filter-class>info.magnolia.cms.filters.MgnlMainFilter</filter-class>
   </filter>
   <filter-mapping>
      <filter-name>magnoliaFilterChain</filter-name>
      <url-pattern>/*</url-pattern>
      <dispatcher>REQUEST</dispatcher>
      <dispatcher>FORWARD</dispatcher>
      <dispatcher>ERROR</dispatcher>
   </filter-mapping>
   -->
   

4. Add the following lines to web.xml in order to register the Groovy Rescue App:

   <servlet>
   <servlet-name>Vaadin</servlet-name>
     <servlet-class>com.vaadin.server.VaadinServlet</servlet-class>
       <init-param>
         <description>Groovy Rescue App</description>
         <param-name>UI</param-name>
         <param-value>info.magnolia.module.groovy.rescue.MgnlGroovyRescueApp</param-value>
      </init-param>
   </servlet>
   <servlet-mapping>
     <servlet-name>Vaadin</servlet-name>
     <url-pattern>/*</url-pattern>
   </servlet-mapping>
   

5. Save web.xml.
6. Start Magnolia.
7. Open a Web browser and access the Groovy Rescue App at http://host/<contextPath>

Make the required changes

Use Groovy commands to navigate to the data you want to change.

In the following example we delete an erroneous configuration node untitled from /config/modules/someModule/virtualURIMapping.

1. Assign Session of config repository to session.

   session = ctx.getJCRSession('config')
   

2. Assign the parent node content to root.

   root = session.getNode('/modules/someModule/virtualURIMapping/')
   

3. Get and remove the child node untitled.

   root.getNode('untitled').remove()
   

4. Save the session.

   session.save()
   

Deregister Groovy Rescue App

1. In web.xml, remove the servlet registration lines you added above.
2. Remove comments from the filter and filter-mapping sections.
3. Save web.xml.

Tomcat should notice that web.xml changed and read the changes automatically. If this does not happen, stop Magnolia, edit web.xml, and start Magnolia again. Then try to access Magnolia.

Access scripts workspace via WebDAV

The WebDAV module supports access to the Groovy scripts workspace. This allows you to use your favorite code editor to create and edit scripts.

Further resources

• groovy Javadocs

• Issue tracker
• More scripts